The present invention relates to a thin film transistor and a related method for manufacturing the same. More particularly, the present invention relates to a thin film transistor and related manufacturing method, in which an on-current is increased to thereby improve the value of an on/off current ratio.
In general, a thin film transistor may be used instead of a load resistor in a 1MB SRAM or higher device. A thin film transistor is also widely used as a switching element for switching an image data signal of each pixel region in a liquid crystal display device.
In the thin film transistor used in the various fields described above, to improve the consumption power of the SRAM cell and, more particularly, to diminish the consumption of power is during a stand-by status and to simultaneously improve memory characteristics, an off-current of the thin film transistor is preferably decreased and an on-current thereof is preferably increased to enlarge the value of the on/off current ratio. To accomplish this purpose, the present inventor has suggested a thin film transistor such as that disclosed in U.S. Pat. No. 5,432,102.
As shown in FIG. 1 of this disclosure, in the above thin film transistor, a gate electrode 12 covered with a gate cap insulating film 13 is formed on an insulating substrate 11. An insulating side wall 16 is formed on one side of gate electrode 12 and cap gate insulating film 13.
A gate insulating film 14 and a semiconductor layer 15 are sequentially formed on substrate 11, gate electrode 12, and cap gate insulating film 13. A channel region C is formed adjacent to the side of gate electrode 12 opposite insulating side wall 16.
Further, associated with semiconductor layer 15, which is connected to the upper portion of channel region C and simultaneously adjacent to insulating film 14 located on gate cap insulating film 13, there are formed an off-set region and an LDD region having a low concentration impurity layer. Drain and source regions are formed on both sides of the channel region, the off-set region, and the LDD region.
According to the above thin film transistor, the off-current is decreased due to the off-set region connected in extended fashion to channel region C and the LDD region of the low concentration layer, thereby increasing the value of the on/off current ratio. However, since there is only one channel in which the on-current flows in the above thin film transistor, the value of the on-current cannot be increased to a great extent. Due to this, the amount that the value of the on/off current ratio can be increased is limited.